The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An internal combustion engine generates power by burning fuel in a combustion chamber in an air media drawn into the chamber. Intake valves are operated by a camshaft in order to intake the air, and the air is drawn into the combustion chamber while the intake valves are open. In addition, exhaust valves are operated by the camshaft, and a combustion gas is exhausted from the combustion chamber while the exhaust valves are open.
Desired operation of the intake valves and the exhaust valves depends on a rotation speed of the engine. That is, a desired lift or desired opening/closing timing of the valves may be determined based on the rotation speed of the engine. In order to achieve the desired valve operation depending on the rotation speed of the engine, various researches, such as designing of a plurality of cams and a continuous variable valve lift (CVVL) that can change valve lift according to engine speed, have been conducted.
In addition, in order to achieve such a desired valve operation depending on the rotation speed of the engine, research has been undertaken on a continuously variable valve timing (CVVT) apparatus that enables different valve timing operations depending on the engine speed. The general CVVT may change valve timing with a fixed valve opening duration.
However, the general CVVL and CVVT are complicated in construction and are expensive in manufacturing cost.
Therefore, a continuous variable valve duration (CVVD) apparatus that can adjust an opening duration of a valve according to an operation state of the engine has been researched.
An exhaust gas recirculation (EGR) apparatus resupplies a portion of exhaust gas exhausted from the combustion chamber to the chamber.
In order to apply the CVVD apparatus and the EGR apparatus to the engine system, a method of diagnosing whether the CVVD apparatus and the EGR apparatus are normally operating is desired.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.